This application claims priority on Japanese Patent Application Number 65021/1999, filed Mar. 11, 1999, the entire disclosure of which is incorporated herein by reference.
1. Technical Field of the Invention
The present invention relates to a gas sealing apparatus for a variable capacity supercharger in which the flow of gas introduced can be adjusted.
2. Prior Art
Variable capacity superchargers in which a plurality of nozzle vanes are assembled, and by changing throats between aforementioned nozzle vanes, a flow of gas introduced into a turbine is controlled, have conventionally been widely used, as shown in FIG. 1, which depicts a typical sample. In detail, turbine housing 1 and compressor housing 2 are assembled into one body via bearing housing 3; turbine impeller 4 in turbine housing 1 and compressor impeller 5 in compressor housing 2 are connected with turbine shaft 7 supported rotatably by bearing 6 in bearing housing 3; annular turbine shroud 9 with gas discharge channel 9a formed on the inner periphery of the shroud is installed with bolts 8 on the inner periphery on the opposite side to bearing housing 3 of above-mentioned turbine housing 1; thus, annular flow channel 10 is formed between axially opposed surfaces of the outer periphery of above-mentioned turbine shroud 9 and the inner periphery of turbine housing 1 on the bearing housing 3 side; in addition, cover 12 provided with gas outlet 11 that communicates with gas discharge channel 9a of aforementioned turbine shroud 9 is installed with bolts 13 to the outer surface on the opposite side to bearing housing 3 in above-mentioned turbine housing 1; gas introduced from gas inlet 14 is led to turbine impeller 4 from scroll channel 15 equipped in turbine housing 1 via aforementioned annular channel 10; and the gas is discharged from gas outlet 11 through gas discharge channel 9a. In this configuration, many nozzle vanes 16 are arranged in annular gas channel 10 between aforementioned scroll channel 15 and the outer periphery of turbine impeller 4; one end of operating shaft 17 is fixed to above-mentioned nozzle vanes 16, and the other end of the shaft protrudes into torque transmission chamber 18 formed between turbine shroud 9 and cover 12 through the outer periphery of turbine shroud 9, and is connected to an actuator via transmission mechanism 19 of a link mechanism type; when the actuator operates, an opening or closing angle of nozzle vanes 16 can be varied; by controlling the opening or closing angle of nozzle vanes 16, throats between each nozzle vane 16 can be adjusted to be wide or narrow; thereby the flow of gas can be changed from a large to a small flow, and vice versa.
In addition, annular recess 20 is formed on the annular channel forming surface of turbine housing 1 with annular channel 10; inside above-mentioned recess 20, ring-shaped clearance control plate 21 is arranged on the wall surface of recess 20 with a predetermined gap S; the position of aforementioned clearance control plate 21, adjustable in the circumferential direction, is fixed by mounting shaft 22 installed on the outer periphery of turbine shroud 9, in which one surface of clearance control plate 21 acts as a surface forming the annular flow channel; thus clearance C to nozzle vanes 16 is maintained at a small constant value.
Although gap S on the rear side of aforementioned clearance control plate 21 is conceptually not necessary, it is actually provided because turbine housing 1 thermally deforms between cold and hot conditions, and there are variations in the accuracy of assembled component parts, however, if gas leaks from this gap S, engine performance at low speed greatly changes, resulting possibly in instability. In particular, when a large volume of gas leaks, nozzle vanes 16 slightly open, and the force for closing nozzle vanes 16 acts due to a pressure difference between upstream and downstream sides of nozzle vanes 16, so that gas flow can no longer be controlled normally.
Therefore, a supercharger for preventing gas leakage and absorbing thermal deformation of turbine housing 1 is proposed (unexamined Japanese patent publication No. 130002, 1989) as shown in FIG. 2; annular recess 20 with large piston ring 23 formed for sealing is mounted on the inner periphery of recess 20; guide annular portion 24 protruding on the rear surface of clearance control plate 21 is engaged with the outer periphery of above-mentioned piston ring 23 for sealing in an axially freely slidable manner; and because guide annular portion 24 engages with piston ring 23 for sealing, gas leakage is prevented and thermal deformation of the turbine housing is absorbed.
However, the apparatus disclosed in the above-mentioned unexamined Japanese patent publication No. 130002, 1989 relates to a large supercharger used for a ship, so the sealing piston ring 23 can be assembled in a space to the rear of clearance control plate 21, but a small supercharger used in a passenger car etc. cannot incorporate a piston ring system because of the limited space available.
An object of the present invention is, therefore, to provide a gas sealing apparatus that can also be adapted to a small supercharger and can reliably seal gas.
To solve the aforementioned problems, according to the present invention, annular turbine shroud (9) is arranged on the inner periphery of turbine housing (1), opposite to bearing housing (3); annular channel (10) is formed between axially opposite surfaces of the above-mentioned turbine shroud and the inner periphery of the turbine housing on the bearing housing side; a large number of nozzle vanes (16) whose opening or closing angle can be adjusted by rotating operating shaft (17) penetrating the outer periphery of the aforementioned turbine shroud, in the above-mentioned annular channel; annular recess (20) is structured on the formed surface of annular channel (10) of the aforementioned turbine housing; in the above-mentioned recess, ring-shaped clearance control plate (21) is fixed on and supported from the turbine shroud side; and clearance C between the front surface of the aforementioned clearance control plate and nozzle vanes is maintained at a predetermined value; in the gas sealing apparatus of a variable capacity supercharger thus constructed, gaskets (25) whose outer rims (25a) of the gaskets are shaped to separate from each other into the form of a round slot of which the section is shaped in the form of a U-shape, and disposed between the rear side of above-mentioned clearance control plate (21) and inner periphery of the bearing housing in turbine housing (1), and using gas pressure, the outer edges are widened and gas is sealed.
Because gaskets are shaped in the form of a U-shape, the gaskets can follow the thermal deformation of the turbine housing, due to the resilience of the gaskets, and at that time, because gas pressure acts to widen the outer rims of the gaskets, a pushing force can be maintained and stable sealing performance is achieved.
In addition, turbine shroud (9) is structured to insert in turbine housing (1) in the axial direction, and is installed on cover (12) of the outer surface of the turbine housing, and seal ring (27) shaped like a piston ring is placed in the axial engagement portion between the above-mentioned turbine shroud and turbine housing.
In this structure, thermal deformation of the turbine housing no longer directly affects the turbine shroud; in addition, leakage of gas from the insert portion between the turbine housing and the turbine shroud is suppressed by the seal ring.
Other objects and advantages of the present invention are revealed in the following description referring to the attached drawings.